The present invention relates in general to data storage systems such as disk drives, and it particularly relates to a thin film read/write head for use in such data storage systems. More specifically, the present invention discloses a new slider design utilizing a high-pitch stiffness air bearing design for smooth media drive applications.
In a conventional magnetic storage system, a thin film magnetic head includes an inductive read/write element mounted on a slider. The magnetic head is coupled to a rotary actuator magnet and a voice coil assembly by a suspension and an actuator arm positioned over a surface of a spinning magnetic disk.
In operation, a lift force is generated by the aerodynamic interaction between the magnetic head and the spinning magnetic disk. The lift force is opposed by equal and opposite spring forces applied by the suspension such that a predetermined flying height is maintained over a full radial stroke of the rotary actuator assembly above the surface of the spinning magnetic disk.
The flying height is defined as the spacing between the surface of the spinning magnetic disk and the lowest point of the slider assembly. One objective of the design of magnetic read/write heads is to obtain a very small flying height between the read/write element and the disk surface. By maintaining a flying height close to the disk, it is possible to record short wavelength or high frequency signals, thereby achieving high density and high storage data recording capacity.
A problem with flying the slider close to the disk surface is that when there is any variation of slider flying height, the possibility of physical interference between the slider and the disk may result in reliability problems and head crashes. Therefore, one objective of the slider design is to maintain a substantially constant flying height close to the disk surface, while minimizing flying height variations when operating the disk drive in a different environment, since variations in head-to-disk spacing may adversely affect signal amplitude and resolution, and may possibly cause head crashes.
An important consideration in slider design for controlling the aerodynamic interaction between the magnetic head and the spinning magnetic disk thereunder, is the air bearing surface. Sliders used in disk drives typically have a leading edge, and a trailing edge at which thin film read/write heads are typically deposited. Generally, sliders have tapered portions at the leading edge and longitudinal side rails that extend from the tapers to the trailing edge.
The tapers may be shaped and of such length as to provide fast pressure buildup during takeoff of the slider from a rest position to a flying height relative to the disk with controlled pitch. The dimensions and shapes of the tapers and side rails are instrumental in determining the flying characteristics of the head. The side rail design determines the pressure generated at the ABS of the slider. In effect, the pressure distribution on the ABS contributes to the flying characteristics of the slider that include flying height, pitch, and roll of the read/write head relative to the rotating magnetic disk.
A conventional magnetic medium, such as a magnetic recording disk, includes a landing zone, which is defined as an annulus area of a width of about 0.5 cm (0.2 in) located at the inner radius of the magnetic disk. The landing zone is made of a non-magnetic material, as its function is not for data recording but is to provide a surface upon which the slider comes to rest in between track seeks during a read/write operation. The surface of the landing zone is typically designed to have a certain degree of roughness so as to prevent stiction between the slider and the disk, and to enable a fast take-off of the slider.
As the continuing trend toward high capacity storage applications currently prevails in this industry, smooth media applications have emerged. A smooth medium disk is characterized by a finely polished surface in its entirety from the outer radius to the inner radius of the disk without a landing zone. The reduced surface roughness allows for lower fly heights, which results in increased data compared to conventional media disks.
The increasing use of smooth media applications, however, poses a technical difficulty with a conventional ABS slider. Because of the low surface roughness of the smooth media disk, the stiction force may increase substantially, thereby preventing the conventional slider from taking off rapidly and smoothly from the surface of the smooth media disk.
To address this problem, sliders have been designed with a dual-etch ABS incorporating Diamond Like Carbon (DLC) pads. In order to maintain a proper trailing edge DLC pad clearance, the slider is required to possess a pitch angle relative to the surface of the disk. The pitch angle is the angle between the planar surface of the media disk and the longitudinal axis of the slider or the arm assembly to which the slider is secured. Because the DLC pads protrude from the surface of the ABS on the slider, it is usually difficult to achieve the clearance between the DLC pads and the surface of the disk.
Without a proper clearance, the DLC pads can come in contact with the surface of the disk, thereby causing physical wear of the disk surface. One conventional method of achieving this clearance is by increasing the leading edge ABS area to raise the pitch angle. Nevertheless, this approach is not entirely satisfactory because the reduction in the leading edge ABS area usually accompanies a lower overall stiffness which can adversely affect the flying characteristics of the slider. Yet, another method of achieving the same objective is to have a relatively deep shallow recession. It, too, fails to provide a desirable solution for achieving the clearance because, in so designed, the gram-load sensitivity and the flying standard deviation of the slider are degraded.
Still another concern arises with the conventional dual-etch ABS slider design. When smooth media disk drives that incorporate rotating smooth media disks and read/write heads with dual-etch ABS sliders are used at relative high altitudes such as 10,000 ft above the sea level, for example, the less air density and ambient pressure adversely affect the slider aerodynamic characteristics which contribute to the flying performance of the dual-etch ABS sliders. Specifically, in the dual-etch ABS slider design, the cavity area is be reduced in order to raise the pitch angle.
Since the lift force is proportional to the cavity area and the ambient pressure, the dual-etch ABS sliders experience a significant reduction in lift at high altitude. Consequently, the flying height of the dual-etch ABS slider substantially decreases from the design flying height, thereby causing the slider to move closer to the surface of the rotating magnetic disk. Hence, this poses a significant concern with a physical interference between the read/write head and the rotating disk that may lead to a head crash or excessive wear of the magnetic disk surface, and thus rendering the disk drive less reliable.
It is thus recognized in light of the above concerns, that there is an unfulfilled need for an improvement in the ABS slider design for smooth media applications. Preferably, the new slider design should provide a necessary DLC pad clearance as required for smooth media applications, without adversely affecting the slider performance characteristics such as ABS stiffness and gram-load sensitivity. Furthermore, the new slider design should exhibit an improved altitude sensitivity.
It is a feature of the present invention to provide a new ABS slider design for use with smooth media applications. The new slider utilizes a triple-etch, high pitch-stiffness side rail ABS design incorporating the following features:
1. A relatively deep shallow recession at the leading edge of the slider, which maximizes the cavity area while at the same time increases the pitch angle to achieve the DLC pad clearance as required by smooth media ABS designs.
2. A shallower recession at the trailing edge of the slider, which provides low gram-load sensitivity and low flying standard deviation.
3. A decreased sensitivity in response to altitude variations.
The foregoing and other features of the present invention are realized by a slider having a generally rectangularly shaped ABS that is bounded by a leading edge, a trailing edge, and two sides. A shallow step region having the shape of the letter xe2x80x9cCxe2x80x9d is formed on the ABS.
The shallow step region is formed by etching the ABS to a depth of approximately 0.25 xcexcm relative to a reference datum. In contrast to the dual-etch ABS slider, the shallow step region of the present ABS design has a greater depth than that of the conventional shallow step region. This greater depth provides the necessary high pitch angle as required to maximize the clearance between DLC pads and the disk.
An ABS region adjoins the shallow step region. The area of the present ABS region is generally smaller than that of the ABS region of a conventional dual-etch ABS slider, thereby making it less susceptible to camber and crown sensitivities due to the respective curvatures in the axial direction from the leading edge to the trailing edge, and in the transverse direction from side to side of the ABS. The reduced camber and crown sensitivities of the ABS region enhance the flying height performance of the triple-etch high pitch-stiffness slider.
A cavity region adjoins the ABS region and has a generally polygonal shape that is formed by etching to a depth that ranges between approximately 50 xcexcm and 80 xcexcm relative to the reference datum of the ABS.